1. Field of the Invention
The present invention relates to an engine generator unit including an engine and an electric-power generators driven by the engine.
2. Related Prior Art
Among general-purpose power supply devices suitable for outdoor use is the so-called engine generator unit which includes an engine and an electric-power generator driven by the engine. The engine and generator would vibrate strongly and become hot during operation of the unit, and thus there have been demands for techniques that can appropriately minimize adverse influences of the vibrations and heat of the engine and generator. Typical example of such an engine generator unit is shown in Japanese Utility Model Laid-Open Publication No. HEI-5-96543.
The engine generator unit disclosed in the Japanese utility model laid-open publication has a crankshaft extending horizontally (in a front-rear direction) through a crankcase of the engine, and an engine-cooling fan fixed to the front end of the crankshaft. The disclosed engine generator unit also includes a recoil starter attached to the front end of the engine-cooling fan device covered with a fan case. Also, in the disclosed engine generator unit, a casing having a stator of the generator attached thereon is connected to a rear end portion of the crankcase, and a rotor of the generator supported at its rear end via bearings is connected to the rear end of the crankshaft. Generator-cooling fan device is provided where the rotor is connected to the rear end of the crankshaft. Further, the engine and generator are supported by a common framework.
However, because both the engine and the generator are supported by the common framework in the disclosed engine generator unit, it is very important to accurately center the generator relative to the crankshaft. Further, due to the fact that the stator-attached casing is supported by the framework and connected to the crankcase, the rotor must be mounted with high positional accuracy relative to such a casing. Furthermore, the provision of the two cooling fan devices, i.e., the engine-cooling fan and generator-cooling fan, would result in an increase in the necessary number of components and a complicated structure.
It is accordingly an object of the present invention to provide an improved engine generator unit which allows the engine and generator to be reliably mounted to a framework with great facility and can effectively cool the engine and generator using a simple structure.
To accomplish the above-mentioned object, the,present invention provides an engine generator unit which comprises: an engine; an electric-power generator to be driven by the engine, the engine and the electric-power generator being provided coaxially in a direction of an engine output shaft, the electric-power generator being an outer-rotor/magnet type generator having a cantilevered outer rotor functioning also as a substitute for an engine fly wheel; a cooling fan device attached to the outer rotor; a fan cover covering the electric-power generator and the cooling fan device, the fan cover being generally in a cylindrical shape and made of die-cast aluminum alloy, the fan cover having, at one end thereof remote from the engine, a cooling-air inlet portion for introducing cooling air from outside the engine generator unit via the cooling fan device, a recoil starter being attached to the cooling-air inlet portion, the fan cover being secured at another end thereof to the engine and having, at the other end, a cooling-air outlet portion for blowing the cooling air onto an outer peripheral surface of the engine; and supporting leg members secured to the fan cover and the engine, the supporting leg member being mounted to a framework via shock-absorbing members.
In the engine generator unit of the present invention, the electric-power generator is supported by the engine in a cantilever fashion, so that both the stator and the rotor of the generator will vibrate together with the engine during operation. Because the electric-power generator is fixed to the framework via the engine and rugged fan cover secured to the engine, it can be supported with sufficient firmness. Even where the engine and fan cover are mounted with some positional error therebetween, as is often the case with this type of engine generator unit, such error can be well accommodated by a gap present between the inner surface of the fan cover and the outer rotor.
Further, the fan cover is made of die-cast aluminum alloy having a high thermal conductivity, and the cooling air drawn in from the outside via the cooling fan continues to be blown onto the inner surface of the fan cover. Because such a fan cover is attached directly to the engine, the fan cover can function as a very efficient heat radiator through which the heat accumulated in the outer wall of the engine can be efficiently radiated to the outside. As a result, the generator and engine can be cooled with increased efficiency and the oil temperature and the like in the engine, can be constantly kept low.
In a preferred implementation of the present invention, the fan cover has a plurality of axial slits formed in an end surface of the cooling-air inlet portion, and the plurality of axial slits of the fan cover and an end surface of the recoil starter together constitute a plurality of air-sucking slits. The plurality of axial slits can be formed with ease simultaneously with formation of the fan cover.
Preferably, the cooling fan device is a centrifugal cooling fan device that forces the cooling air from the outside into between the outer rotor and the fan cover so as to send the cooling air to the engine and a vicinity thereof. The cooling air forced into between the outer rotor and the fan cover can also effectively cool the inner peripheral surface of the fan cover.